There are many applications in which it is desirable to filter fluids in a mechanical system. For example, internal combustion engines, vehicle transmissions, and gear boxes often contain a sump having motor oil or another suitable lubricant.
Some systems use a pump to circulate fluid and pump the fluid through a filter as it is circulated. However, even in pump-based systems, there are sometimes areas inside the fluid handling system where the fluid tends to collect without flowing and in these areas it can be desirable to provide additional filtration.
Furthermore, there are many mechanical systems that utilize lubricating, cooling and/or hydraulic fluids where the fluid is not actively circulated by a pump. In some of these systems, no pump is provided, and the fluid circulates merely based on motion imparted by internal moving components and/or temperature gradients. In these system, it is still desirable to have some way of removing contaminants, particularly metallic particulate contaminants, from the fluid. Examples of these systems include many types of gear boxes, including for example automotive differential casings.
Metal particulate contaminants often occur due to wear in mechanical systems. It is desirable to remove these from the systems so that they do not cause even further wear. While these particles sometimes fall out of suspension by sedimentation, mere sedimentation is often not enough to clear the particles. Also, even when the particles do fall out by sedimentation, a disturbance in the fluid such as by vibration can re-introduce the particles into the fluid.
Thus, there are many mechanical systems that would benefit from the ability to filter undesirable particles, including especially metallic particles, from the fluid, such as lubricating oil, differential fluid, transmission fluid, power fluid, brake fluid, anti-freeze, or any other type of fluid used in a mechanical system.
Heretofore, it has been known to simply mount a piece of solid magnetic material onto an inside surface of the fluid-containing housing. This piece of solid magnetic material attracts magnetic particles from the fluid in the vicinity of the magnet, and these particles move toward the magnet. As the particles come closer to the magnet, the magnetic force increases, thereby pulling the particles further toward the magnet until they adhere to the surface of the magnet. At this point, the particles generally tend to remain on the surface of the magnet due to the strong magnetic field on the surface of the magnet.
A disadvantage of the above-described arrangement is that the particles are merely adhered to the magnet by the magnetic force. It has been found in some instances that the particles will become relatively easily dislodged from the magnet, and will re-enter the fluid undesirably. For example, a sudden impact or jolt as is often experienced by automotive components, can loosen the metallic particles. Further, as the time of use of the filter increases, the surface area of the magnet tends to become covered with magnetic particles, and thus a film of particles can be created which tends not to retain further particles.
Another disadvantage with the use of a solid magnetic material by itself is that where the magnet is near a relatively high fluid flow or fluid movement region, the particles may only be initially attracted towards the magnet, but due to the fluid flow in the vicinity of the magnet may be carried past the magnet and not actually adhere to it. Also, in areas of high fluid flow, the particles tend to become dislodged more easily from the magnet by vibration.
From the foregoing, it can be seen that there is a need in the art for a magnetic filtration system that overcomes at least in part some of the above problems. In particular, there is a need in the art for a magnetic fluid filter arrangement that can not only desirably attract but also retain metallic particles from a fluid, even when the fluid is flowing past the filter assembly.